SPE Library

Blends of Polyethylene terephtalate (PET) and Linear Low Density Polyethylene (LLDPE) compatibilized with maleic anhydride-grafted-LLDPE (MAH-g-LLDPE) were characterized. The addition of MAH-g-LLDPE produced a fine dispersed phase morphology and improved processability of blends. A decrease on the crystallization temperature and on the degree of crystallinity of the polyester and an increase on the elastic modulus and on the stress at break were observed. These effects could be attributed to the reduced interfacial tension as a result of the promoted interaction between the polymers by the functionalized polymer.

The effect of chemical exposure on the stress rupture behavior of polyurethane, polyacetal and four acrylic materials was investigated. The polyurethane and polyacetal stress rupture data was used to provide the basis for verification of the expected service life of products made from these materials. The stress rupture data from four different acrylic materials was used to differentiate the materials on the basis of long term strength. The stress rupture data (applied stress vs. failure time) was obtained using a custom designed and built constant tensile load (CTL) testing apparatus.

Polyetheramide tri-block copolymers have been polymerized in a modular counter-rotating twin screw extruder under a range of processing conditions, including temperature profiles and screw speeds. Polyetheramide tri-block copolymers had not been previously polymerized in a twin screw extruder. Thermal analysis and viscosity measurements clearly demonstrated that the formed copolymers have two separated domains arising from two different block segments. Studies were also made of melt spinning polyetheramide tri-block copolymer into oriented filaments. The formed filaments were characterized using birefringence. The melt spun fibers of polyetheramide tri-block copolymer showed higher elongation than those of polyamide 6 due to the existence of elastomers.

When numerically analyzing mixing in polymer processes, there are several difficulties that the engineer will encounter; such as moving boundaries, complex geometries and non-linear material behavior. The Boundary Element Method (BEM), as a technique which requires only boundaries (surfaces) to be meshed, is ideal to simulate problems with moving boundaries and complex geometries. However, the introduction of non-linear material behavior requires domain information. This study applies the Monte Carlo technique to integrate the domain and keep the boundary-only discretization. Results show the influence of non-linear effects, such as shear-thinning viscosity, when characterizing mixing in polymer processing equipment.

The dimensional stability, such as shrinkage strain or stress, of oriented films and sheets is an important factor in the application of these articles. High shrinkage may be desired for some applications or need to be minimized for others. Thus shrinkage control and monitoring is of paramount importance. On the other hand, it is well established for most polymer melts that the birefringence is simply related to the stress through the stress optical rule, and simple theories relate the stress and birefringence to the strain. In this paper, we investigate these relationships for oriented amorphous (polystyrene, PS) and semi-crystalline polymers (PE, PET, and sPS) in relation with their shrinkage stress and/or strain. For low orientations, it is found that the stress and strain can be simply related to birefringence. For semicrystalline polymers, the relationship is more complex. At high degrees of orientation, some modifications to the theories are required.

A high Tg, aromatic nylon oligomer based on poly (tolyleneisophthalamide) (TDAI) was designed and evaluated as an additive for melt blending with conventional aliphatic nylons (PA 6 and PA66) to achieve miscible blends with improved Tg and property retention upon moisture equilibration. Blending only 10w% of TDAI in GF-PA6 and GF-PA66, a nearly complete retention of modulus and strength could be achieved at 50%RH, validating the general concept of wet Tg enhancement of nylons through miscible Tg-boosting additives. Moisture insensitive oxygen barrier properties could also be obtained in cast PA6 film. The oligomeric nature of TDAI contributes to improved melt flow in PA 6 and permits higher glass loading to give products with moisture-insensitive stiffness and dimensional stability.

Nylon 6 nanocomposites consisting of extremely thin, nanometer scale dispersions of platelet type silicates have been prepared and their injection molded properties and morphology have been investigated. The high surface area of such silicate dispersions contribute to a high reinforcement efficiency at low loadings, resulting in high specific modulus, strength and DTUL. However, such ultra-thin platelets cause some unusual structure development during the injection molding. Flow induced orientation of the platelets and an apparent surface nucleation promotes faster crystallization of nylon 6. Higher crystallinity was observed in the nylon 6 nanocomposites, particularly at the surface and in thin-wall moldings compared to the conventional nylon 6. The crystallization, skin-core morphology effects in the injection molded nylon 6 nanocomposites correlate well with the observed mechanical properties, weld-line and surface UV/ weathearing behavior.

During the cure of a thermoset-thermoplastic blend two-phase morphologies may be formed. The phase separation process can be controlled by manipulation of the rate of polymerization of the thermoset system. In this work, the effect of the addition of different amounts of polycarbonate (PC) on the rheokinetics of an epoxy thermoset system is presented. The reactive system used was diglycidyl ether of bisphenol-A cured with 4-4 diaminodiphenylsulfone. The blends of the PC and the epoxy resin were prepared using two different procedures: (a) hot melt blending and (b) dissolution in a common solvent. The kinetics was followed by differential scanning calorimetry and the change in the rheological properties during the curing by dynamic rheometry.

The compatibility of individual homopolymers is one of the most important parameters influencing polymer blending. Often times blending involves components with vastly different viscosities and interfacial tensions. Supercritical carbon dioxide can be added to polymer melts as a processing aid such that effective polymer blending will occur. A blend system of a high viscosity polymethylmethacrylate (PMMA) and low viscosity polystyrene is analyzed in this work. Carbon dioxide has a higher affinity for PMMA than for polystyrene (1). Therefore, a greater plasticizing effect will occur for the PMMA than for the polystyrene. The improved results in polymer blending will be shown in this work. The morphology development of the polymer blends is analyzed in a high-pressure batch mixer and the continuous extrusion process.

Rheological analysis of multi-phase systems is very difficult because the morphology is strongly related to the flow history. The small amplitude oscillatory shear flow does not affect the morphology and is very useful to predict the viscoelastic behavior of immiscible blends. In this work we study the dynamic rheological properties of Polypropylene based ternary blends with linear low density polyethylene and ethylene/propylene terpolymers of different viscosities taking into account the effects of changing the composition and concentration of the dispersed phase. The predictions of a constitutive equation for emulsions of viscoelastic fluids are also included.

Simultaneous thermal analysis techniques, for example TG-DSC/DTA (Thermogravimetric-Differential Scanning Calorimetry/Differential Thermal Analysis), yield vital information on polymer makeup based on heat flow behavior and mass change characteristics during heating. These techniques offer little direct information, however, on exact composition of evolved gas products. It has recently been found quite powerful to combine simultaneous thermal analyzers directly in tandem with both Mass and FTIR (Fourier Transform Infrared) spectrometers. The challenge is effectively coupling the instruments such that optimized evolved gas analysis is possible. Practical applications of evolved gas analysis for polymeric materials include analysis of decomposition and aging processes, additives, residues, outgassing, desorption behavior and more. This paper will examine results of thermoanalytical experiments on polymeric materials via TG-DSC/DTA closely coupled with both a quadrupole mass spectrometer (QMS) and an FTIR spectrometer.

Proper characterization of polymers by Differential Scanning Calorimetry (DSC) may be compromised when calorimetric transitions coincide or when components volatilize at the same time as critical transitions are expected to occur. To increase the utility of DSC for polymer characterization, it is highly desirable to minimize system time constant and improve signal-to-noise ratio in order to improve sensitivity and peak resolution. As well, operation under conditions of increased pressure may succeed in preventing unwanted volatilization, permitting resolution of certain transitions. This paper describes in detail specific polymer applications emphasizing the significance of DSC cell time constant reduction in terms of improved peak resolution as well as the importance of cell baseline stability throughout a broad temperature range and over increasing pressure conditions.

Liquid dialkylperoxydicarbonates are used as initiators in the PVC industry. Due to the thermal reactivity of these initiators, they require very low temperature storage, shipment and handling. At temperatures above 10°C, most undergo auto-accelerated self-induced decomposition. In other words, their self-accelerating decomposition temperature (SADT) is exceeded. New additives have been discovered which increase the SADT of the initiators. These additives effectively stabilize the product, making them safer to handle, store, and ship. The proprietary additives and a mechanism of stabilization will be discussed. We will also include a section concerning the implications these products have for future initiator formulation.

Fish oil or conjugated fish oil was copolymerized with divinylbenzene and norbornadiene or dicyclopentadiene using BF3·OEt2 as an initiator in an effort to develop useful biodegradable polymers with rationally designed structures from natural renewable resources. Dynamic mechanical analysis, DSC, TGA and nuclear magnetic resonance spectroscopy have been used to characterize the resulting fish oil polymers. The results show that viable fish oil products ranging from rubbers to hard plastics may be synthesized by changing the type and amount of the comonomers used. The fish oil products are thermosetting polymers having highly crosslinked structures, glass transition temperatures ranging from 50 to 130°C, room temperature modulus of about 109 Pa, and excellent thermal stability, making the products useful for applications where current biodegradable plastics are not useable.

We report a method for making novel, lightweight (0.3-1.1 kg/dm3) polymer composites based on high-temperature foam polyimide binder, carbon fiber or organic fiber felt. The density and mechanical properties of the foam composite can be varied over a wide range, depending on the volume contents of the fiber and air pores. The thermal degradation temperature of the foam composite is around 570°C, and thermolysis products of foam binder are comparable to those of wood. The combination of excellent thermal stability, superior specific mechanical properties, exceptional flame resistance of polyimides, and facile processing of the foam composites can provide unusual performance for new design of advanced materials and structures.

The effect of coupling agents and particle size on melt rheology of polyphenylene sulfide-bonded neodymium-iron- boron (Nd-Fe-B) alloy magnets was studied with oscillatory flow experiments to accelerate efforts to optimize their processing. The minimum viscosity of the polymer-bonded magnets near 290°C was obtained with Nd-Fe-B fillers (106-150 particle size range) that were coupled with a silane coupling agent. All the samples tested followed power-law fluid flow behavior. Morphological and dynamic mechanical analysis of the samples showed that the beneficial function of the coupling agent may be ascribed to enhanced wetting of the magnetic Nd-Fe-B powders by the polymer, improving the processability of the polymer bonded magnets.

This research is directed at the thermal processing and physical characterization of films derived from natural proteins, viz. soy, corn-zein, egg white and beef-broth. Twin screw extrusion was employed for pre-process compounding of proteins and the plasticizer. The thermal processing was accomplished with compression molding (a batch process) and extrusion (a continuous process). Single component soy films were light yellow in color, translucent, flexible and well consolidated, with a thickness of approximately 300µm. The tensile strength of these films was about 3 MPa. Continuous chill-roll film extrusion was also carried out and the process is being refined.

It is well recognized that Ultrahigh Molecular Weight Polyethylene(3.6x106) (UHMWPE) has been used as a component in joint prostheses for over 95 years. Essentially all fabricated UHMWPE during this period has exhibited incomplete fusion and/or severe molecular weight degradation. It is most likely that these features have compromised the potential wear resistance as well as the mechanical properties of this material. By fabricating UHMWPE in a vacuum, complete densification without fusion defects while maintaining the 3-4 million starting molecular weight was achieved. This paper discusses the results of the vacuum fabrication of UHMWPE.

The ability to procure rapid tooling for plastic molding and other near-net shape forming processes remains one of the largest technical challenges facing our manufacturing industry today. Advances in rapid prototyping and desk top manufacturing e.g., selective laser sintering, solid free forming, ....., etc have cut lead-times by as much as and are capable of producing relatively precise tooling which requires minor secondary machining. This paper presents a new technology developed by AlliedSignal which is capable of fabricating metal and ceramic components via powder injection molding, as well as the added capability of producing hard tooling from soft tooling.

Due to their poor heat-resistant properties, polymer bonded magnets are limited in their applications in aggressive environment. By using high temperature engineering polymers the heat-resistance of polymer bonded magnets can be significantly improved. However, the extreme tendency for thermal oxidation of Nd-Fe-B alloy powder limits the use of high temperature polymers. This paper discusses the application of silane coupling agents to the thermoplastic polymer bonded Nd-Fe-B magnets. The results show that after the treatment of coupling agent, the thermal stability and oxidation/corrosion resistant properties of the Nd-Fe-B alloy powder at high temperature improved significantly, making it usable for high-temperature processing and high-temperature application. An enhanced wetting of the Nd-Fe-B particles in polymer matrix has been observed. The bonding between the Nd-Fe-B powders and polymer matrix was improved by the coupling agents. In turn, the enhanced bonding between the powder and the polymer dramatically increased the mechanical properties of polymer-bonded Nd-Fe-B magnets.